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authorChristian Brauner <brauner@kernel.org>2022-04-04 12:51:40 +0200
committerMiklos Szeredi <mszeredi@redhat.com>2022-04-28 16:31:10 +0200
commit00675017e0aeba5305665c52ded4ddce6a4c0231 (patch)
treef45cf7c4d720e8e5e00b63b86c86f48e36871fa1 /fs/namei.c
parent3123109284176b1532874591f7c81f3837bbdc17 (diff)
fs: add two trivial lookup helpers
Similar to the addition of lookup_one() add a version of lookup_one_unlocked() and lookup_one_positive_unlocked() that take idmapped mounts into account. This is required to port overlay to support idmapped base layers. Cc: <linux-fsdevel@vger.kernel.org> Tested-by: Giuseppe Scrivano <gscrivan@redhat.com> Reviewed-by: Amir Goldstein <amir73il@gmail.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Diffstat (limited to 'fs/namei.c')
-rw-r--r--fs/namei.c70
1 files changed, 60 insertions, 10 deletions
diff --git a/fs/namei.c b/fs/namei.c
index 3f1829b3ab5b..5f91d526a86e 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2768,7 +2768,8 @@ struct dentry *lookup_one(struct user_namespace *mnt_userns, const char *name,
EXPORT_SYMBOL(lookup_one);
/**
- * lookup_one_len_unlocked - filesystem helper to lookup single pathname component
+ * lookup_one_unlocked - filesystem helper to lookup single pathname component
+ * @mnt_userns: idmapping of the mount the lookup is performed from
* @name: pathname component to lookup
* @base: base directory to lookup from
* @len: maximum length @len should be interpreted to
@@ -2779,14 +2780,15 @@ EXPORT_SYMBOL(lookup_one);
* Unlike lookup_one_len, it should be called without the parent
* i_mutex held, and will take the i_mutex itself if necessary.
*/
-struct dentry *lookup_one_len_unlocked(const char *name,
- struct dentry *base, int len)
+struct dentry *lookup_one_unlocked(struct user_namespace *mnt_userns,
+ const char *name, struct dentry *base,
+ int len)
{
struct qstr this;
int err;
struct dentry *ret;
- err = lookup_one_common(&init_user_ns, name, base, len, &this);
+ err = lookup_one_common(mnt_userns, name, base, len, &this);
if (err)
return ERR_PTR(err);
@@ -2795,6 +2797,59 @@ struct dentry *lookup_one_len_unlocked(const char *name,
ret = lookup_slow(&this, base, 0);
return ret;
}
+EXPORT_SYMBOL(lookup_one_unlocked);
+
+/**
+ * lookup_one_positive_unlocked - filesystem helper to lookup single
+ * pathname component
+ * @mnt_userns: idmapping of the mount the lookup is performed from
+ * @name: pathname component to lookup
+ * @base: base directory to lookup from
+ * @len: maximum length @len should be interpreted to
+ *
+ * This helper will yield ERR_PTR(-ENOENT) on negatives. The helper returns
+ * known positive or ERR_PTR(). This is what most of the users want.
+ *
+ * Note that pinned negative with unlocked parent _can_ become positive at any
+ * time, so callers of lookup_one_unlocked() need to be very careful; pinned
+ * positives have >d_inode stable, so this one avoids such problems.
+ *
+ * Note that this routine is purely a helper for filesystem usage and should
+ * not be called by generic code.
+ *
+ * The helper should be called without i_mutex held.
+ */
+struct dentry *lookup_one_positive_unlocked(struct user_namespace *mnt_userns,
+ const char *name,
+ struct dentry *base, int len)
+{
+ struct dentry *ret = lookup_one_unlocked(mnt_userns, name, base, len);
+
+ if (!IS_ERR(ret) && d_flags_negative(smp_load_acquire(&ret->d_flags))) {
+ dput(ret);
+ ret = ERR_PTR(-ENOENT);
+ }
+ return ret;
+}
+EXPORT_SYMBOL(lookup_one_positive_unlocked);
+
+/**
+ * lookup_one_len_unlocked - filesystem helper to lookup single pathname component
+ * @name: pathname component to lookup
+ * @base: base directory to lookup from
+ * @len: maximum length @len should be interpreted to
+ *
+ * Note that this routine is purely a helper for filesystem usage and should
+ * not be called by generic code.
+ *
+ * Unlike lookup_one_len, it should be called without the parent
+ * i_mutex held, and will take the i_mutex itself if necessary.
+ */
+struct dentry *lookup_one_len_unlocked(const char *name,
+ struct dentry *base, int len)
+{
+ return lookup_one_unlocked(&init_user_ns, name, base, len);
+}
EXPORT_SYMBOL(lookup_one_len_unlocked);
/*
@@ -2808,12 +2863,7 @@ EXPORT_SYMBOL(lookup_one_len_unlocked);
struct dentry *lookup_positive_unlocked(const char *name,
struct dentry *base, int len)
{
- struct dentry *ret = lookup_one_len_unlocked(name, base, len);
- if (!IS_ERR(ret) && d_flags_negative(smp_load_acquire(&ret->d_flags))) {
- dput(ret);
- ret = ERR_PTR(-ENOENT);
- }
- return ret;
+ return lookup_one_positive_unlocked(&init_user_ns, name, base, len);
}
EXPORT_SYMBOL(lookup_positive_unlocked);